1. Field of the Invention
The present invention relates to data communications, and, more particularly, efficiency in determining control signals in data communication circuits that include concatenated payloads.
2. Description of the Related Art
A data communications network is the interconnection of two or more communicating entities (i.e., data sources and/or sinks) over one or more data links. A data communications network allows communication between multiple communicating entities over one or more data communications links. High bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic. In the future, these demands are certain to increase. To meet such demands, an increasingly popular alternative is the use of lightwave communications carried over fiber optic cables. The use of lightwave communications provides several benefits, including high bandwidth, ease of installation, and capacity for future growth.
The synchronous optical network (SONET) protocol is among those protocols designed to employ an optical infrastructure and is widely employed in voice and data communications networks. SONET is a physical transmission vehicle capable of transmission speeds in the multi-gigabit range, and is defined by a set of electrical as well as optical standards.
In some networks, network nodes store data which they use for proper operation. In SONET, data between adjacent nodes are transmitted in modules called STS's (synchronous transport signals). Each STS is transmitted on a link at regular time intervals (for example, 125 microseconds). See GR-253 (GR-253: Synchronous Optical Network (SONET) Transport Systems, Common Generic Criteria, Issue 2 [Bellcore, December 1995] (hereinafter referred to as GR-253 Specification) incorporated herein by reference for all purposes. An STS-1 is a Synchronous Transport Signal-level 1 is the basic module in SONET and is defined as a specific sequence of 810 bytes (6480 bits) including overhead bytes and an envelope capacity for transporting payloads. In general, the higher-level signals, the STS-N signals, are lower-level modules that are multiplexed together and converted to an OC-N or STS-N signal. An STS-N frame is a sequence of N×810 bytes wherein N is a predetermined number. An STS-N is formed by byte-interleaving of STS-1 and STS-M modules, wherein M is less than N.
In some systems, such as certain ISDN and ATM systems, multiple STS-1 payloads are transported as super rate payloads. To accommodate such a payload an STS-Nc module is formed by linking N constituent STS-1s together in fixed phase alignment. The payload is then mapped into a single STS-Nc Synchronous Payload Envelope (SPE) for transport. Network equipment supporting the multiplexing, switching or transport of STS-Nc SPES treat an STS-Nc SPE as a single entity. When an STS-Nc SPE is treated as a single entity, concatenation indicators are present in the second through the Nth STS payload pointers which show that the STS-1s in the STS-Nc are linked together.
STS-Ncs can exist in many different combinations in an STS-M payload. One problem with concatenated STS signals includes connecting an combination of STS-Ncs within an STS-M payload in a manner that is a working combination of STS-Ncs.
Furthermore, an efficient method of connecting multiple STS-1s in an STS-M payload is needed.